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In vitro activity of a new ketolide antibiotic, HMR 3647, against Chlamydia pneumoniae
1Department of Pediatrics, SUNY Health Science Center at Brooklyn, New York 11203, USA.
Abstract:
The in vitro activities of HMR 3647, roxithromycin, erythromycin, and azithromycin against 19 strains of Chlamydia pneumoniae were tested. The MIC at which 90% of the isolates are inhibited and the minimum bactericidal concentration at which 90% of the isolates are killed of HMR 3647 were 0.25 microgram/ml (range, 0.015 to 2 micrograms/ml). Nine recently obtained clinical isolates from children with pneumonia were more susceptible (MICs, 0.015 to 0.0625 microgram/ml) than older strains that had been passaged more extensively.
Insights
HMR 3647 demonstrates potent in vitro activity against Chlamydia pneumoniae, showing effectiveness in inhibiting and killing bacterial strains. Recently isolated strains from children with pneumonia were found to be more susceptible to HMR 3647.
Area of Science:
- Microbiology
- Pharmacology
- Infectious Diseases
Background:
- Chlamydia pneumoniae is a significant cause of respiratory infections, including pneumonia.
- Macrolide antibiotics are commonly used for treating C. pneumoniae infections.
- Evaluating novel or existing antibiotics against C. pneumoniae is crucial for effective treatment strategies.
Purpose of the Study:
- To assess the in vitro antimicrobial activity of HMR 3647 against Chlamydia pneumoniae.
- To compare the efficacy of HMR 3647 with other macrolides like roxithromycin, erythromycin, and azithromycin.
- To investigate potential differences in susceptibility based on bacterial strain history.
Main Methods:
- Determined the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) for HMR 3647.
- Tested 19 strains of Chlamydia pneumoniae, including recently isolated clinical strains and older passaged strains.
- Compared MIC values of HMR 3647 against roxithromycin, erythromycin, and azithromycin.
Main Results:
- HMR 3647 exhibited potent activity, with MIC90 and MBC90 values of 0.25 microgram/ml (range: 0.015 to 2 microgram/ml).
- Recently isolated clinical strains from pediatric pneumonia cases showed higher susceptibility to HMR 3647 (MICs: 0.015 to 0.0625 microgram/ml).
- Older strains, subjected to extensive passaging, were less susceptible compared to recent isolates.
Conclusions:
- HMR 3647 is a highly active agent against Chlamydia pneumoniae in vitro.
- The susceptibility of C. pneumoniae to HMR 3647 may be influenced by strain history and passage.
- HMR 3647 shows promise as a potential therapeutic agent for C. pneumoniae infections, particularly in pediatric pneumonia.